1. Field of the Invention
This invention relates to a dry image forming material. More particularly, it relates to a dry image forming material having good image stability.
2. Description of the Prior Art
Conventional image forming materials using a silver salt need a very complicated wet process of forming image thereon. In order to simplify the image forming process, there have been proposed photosensitive materials comprising an organic silver salt oxidizing agent, a reducing agent for silver ion and a small amount of a silver halide on which images can be formed only by dry processing. However, the images obtained by such dry processes cannot be stored for a long period of time, undesirable darkening of the background of images gradually occurs to lose the contrast. In order to avoid this disadvantage, there have been made many attempts. For example, U.S. Pat. Nos. 3,707,377 and 3,874,946 describe the use of 1,2,3,4-tetrabromobutane, tribromoquinaldine and 2-tribromomethylsulfonyl benztriazole as a background-darkening preventive agent for dry processing photosensitive materials. However, the background-darkening preventive effect of these compound is still insufficient. Furthermore, many of these compounds either reduce the stability of the photosensitive materials or discolor the background of images to yellow, and the stability of these compounds is too low to provide good image stability with the image forming materials.